I'd be careful given that middle schoolers will have very little context for the people you're trying to introduce. It's hard to truly understand why, say Roosevelt is a leader if you don't understand WWII or even really know what it was.

If I was trying to teach a course on leadership I'd focus on practical aspects and some experiential activities. This would seem more effective and more practical to the students in their lives. Have them comprehend some type of leadership theory and then apply it in some kind of fun activity. Obstacle courses or treasure hunt or something physical would be great.

source: I'm a middle school teacher